U.S. patent number 6,363,896 [Application Number 09/673,772] was granted by the patent office on 2002-04-02 for camshaft adjuster for internal combustion engines.
This patent grant is currently assigned to DaimlerChrysler AG. Invention is credited to Wolfgang Speier.
United States Patent |
6,363,896 |
Speier |
April 2, 2002 |
Camshaft adjuster for internal combustion engines
Abstract
A camshaft adjuster (1) for internal combustion engines has a
central tensioning screw (9) for fixing the adjuster (1) in
relation to a camshaft (2). A slide (8) controls the supply of the
pressure medium to the camshaft adjuster (1) being integrated into
the tensioning screw (9). The tensioning screw (9) forms the
mounting of the camshaft adjuster (1) in relation to the camshaft
(2).
Inventors: |
Speier; Wolfgang (Stuttgart,
DE) |
Assignee: |
DaimlerChrysler AG (Stuttgart,
DE)
|
Family
ID: |
7865014 |
Appl.
No.: |
09/673,772 |
Filed: |
July 5, 2001 |
PCT
Filed: |
April 14, 1999 |
PCT No.: |
PCT/EP99/02495 |
371
Date: |
July 05, 2001 |
102(e)
Date: |
July 05, 2001 |
PCT
Pub. No.: |
WO99/54599 |
PCT
Pub. Date: |
October 28, 1999 |
Foreign Application Priority Data
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Apr 18, 1998 [DE] |
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198 17 319 |
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Current U.S.
Class: |
123/90.17;
74/568R |
Current CPC
Class: |
F01L
1/344 (20130101); F01L 1/3442 (20130101); F01L
2001/34426 (20130101); F01L 2001/3443 (20130101); Y10T
74/2102 (20150115) |
Current International
Class: |
F01L
1/344 (20060101); F01L 001/344 () |
Field of
Search: |
;123/90.15,90.17,90.31
;74/568R ;464/1,2,160 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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40 29 849 |
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Mar 1991 |
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DE |
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39 37 644 |
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May 1991 |
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DE |
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196 11 365 |
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Sep 1997 |
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DE |
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197 26 300 |
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Jan 1998 |
|
DE |
|
92/20906 |
|
Nov 1992 |
|
WO |
|
Primary Examiner: Lo; Weilun
Attorney, Agent or Firm: Kenyon & Kenyon
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is the national phase filing of PCT/EP99/02495
filed Apr. 14, 1999, which claims priority to German Patent
Application 198 17 319.9 filed Apr. 18, 1998, which applications
are herein expressly incorporated by reference.
Claims
What is claimed is:
1. A camshaft adjuster for internal combustion engines, which is
situated in the drive for driving a camshaft by means of the
crankshaft and is to be connected to the camshaft in a centered and
coaxial manner with respect to the latter, comprising:
an inner element which is fixed in terms of rotation relative to
the camshaft is penetrated by a central clamping screw and can be
clamped axially against the camshaft by means of this screw;
an outer element which can be turned relative to the inner element
and via which the drive connection to the crankshaft runs;
an accommodation space between the inner element and the outer
element for hydraulically pressurizable actuating means for turning
the outer element relative to the inner element; and
a control device associated with these actuating means and having a
multi-way valve integrated into the clamping screw, which, as a
housing, forms an axial receptacle for a centrally situated and
axially displaceable control spool, the clamping screw carrying the
inner element engages by its camshaft end in an axial centering
collar on the camshaft and is supported against the latter.
2. The camshaft adjuster according to claim 1, wherein the inner
element and the outer element are designed with flat end faces and
are covered over a certain area by annular covers.
3. The camshaft adjuster according to claim 2, wherein the annular
covers adjoin the centering collar of the camshaft radially on the
inside.
4. The camshaft adjuster according to claim 1, wherein the control
spool is connected to the armature of an actuator arranged fixed
relative to the housing and comprising an actuating magnet.
Description
BACKGROUND OF THE INVENTION
The invention relates to a camshaft adjuster for internal
combustion engines.
Camshaft adjusters are known in the form of piston-type adjusters
with an axially displaceable piston (DE 40 29 849 C2, DE 196 11 365
A1 and DE 197 26 300 A1) and in the form of vane-type adjusters
with vanes that can be acted upon and pivoted in the
circumferential direction. In connection with both designs, the
camshaft adjuster is fixed as an end-mounted extension of the
camshaft by means of a central clamping screw.
For the purpose of controlling the hydraulic pressure supply to the
camshaft adjuster, DE 40 29 849 C2 discloses the provision of an
external 4/2-way valve, from which supply passages run to the
camshaft and to the actuating piston that is provided here as the
actuating means and is arranged in an accommodation space between
the inner element and the outer element, the drive connection to
the crankshaft running via the outer element.
The long conduit paths that this entails, with the risk of
corresponding leaks and of a certain elasticity, can have the
effect that the system has inadequate hydraulic rigidity and thus
makes satisfactory control more difficult, not to mention the fact
that the external arrangement of the control device formed by the
directional control valve has a negative effect in terms of the
outlay on construction and the size of the installation space
required.
DE 196 11 365 A1 discloses integration of the control device
designed as a multi-way valve into the clamping screw. The result
is that the latter acts as a housing to form an axial receptacle
for a centrally situated and axially displaceable control spool via
which pressure medium can be supplied to the actuating means
radially along short paths.
In view of this, provision is made to guide the camshaft adjuster's
inner element, which is fixed in terms of rotation relative to the
camshaft, the camshaft adjuster's outer element, which can be
turned relative to the inner element and via which the drive
connection to the crankshaft runs, on the clamping screw,
irrespective of centering of the inner element relative to the
camshaft independently of this. This requires very narrow
tolerances, that is to say a high outlay on manufacture, and
furthermore leads to misalignment errors due to the cumulative
effect of a number of radial guides subject to play, these errors
potentially having disadvantageous effects on concentricity of
running and vibration, such concentricity and misalignment errors
also make it more difficult to operate the control spool by means
of the axially offset actuating magnet as actuator, associated with
the spool on the housing side, with the minimum clearance relative
to the armature carried by the control spool. However, larger
clearances lead to a need for more power and hence for more space,
and, given the conditions of construction in the case of internal
combustion engines for motor vehicles, this is often not available,
if only because of the axial extension entailed by the camshaft
adjuster.
SUMMARY OF THE INVENTION
The object of the present invention is to construct a camshaft
adjuster of the type stated at the outset in such a way that
optimum centering of the camshaft adjuster is achieved. This
centering simultaneously creates the conditions for particularly
simple and economical manufacture.
According to the invention, this is achieved by the clamping screw
forming the element of the camshaft adjuster that effects centering
relative to the camshaft, eliminating the need to provide the
adjuster with any further centering support as regards its inner
and outer element and its lateral closure elements in the form of
covers. This eliminates the need for axial undercuts or projections
on the inner and outer elements, which would make manufacture more
difficult. Moreover, the configuration according to the invention,
involving centering of the entire camshaft adjuster, including the
connection of the control device formed by the multi-way valve to
the actuator, by means of the clamping screw, creates particularly
favorable conditions for largely tolerance-free centering without
excessive demands as to manufacture, with ideal conditions for
optimum, vibration-free concentricity of running and with the
minimum required clearances at the transition between the control
spool and the actuator.
As a refinement of the invention, the inner element and the outer
element can be designed with flat end faces, that is to say form
disc-shaped elements, which are covered over a certain area by
annular covers, with the result that the covers require only axial
clamping. It has proven expedient here if the covers adjoin the
centering collar of the camshaft radially on the inside, providing
sufficient radial overlap with the inner and outer elements to
allow the use of simple sealing means in so far as these are to be
used, the precise centering with small clearances achieved by means
of the invention also having an advantageous effect as regards the
reduction of leakage.
The refinement according to the invention of using disc-shaped
inner and outer elements and covers leads to particularly
far-reaching simplifications in the case of camshaft adjusters
designed as vane-type adjusters.
From the following detailed description, taken in conjunction with
the drawings and subjoined claims, other objects and advantages of
the present invention will become apparent to those skilled in the
art.
BRIEF DESCRIPTION OF THE DRAWINGS
Further details and features of the invention will become apparent
from the claims. The invention will furthermore be explained with
additional details by means of the drawings in which:
FIG. 1 is a partially schematic longitudinal section view through a
camshaft adjuster according to the invention, along the line I--I
in FIG. 2;
FIG. 2 is a section view along line II--II in FIG. 1; and
FIG. 3 is a view substantially similar enlarged representation of
the central area of the camshaft adjuster shown in FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The camshaft adjuster shown in FIGS. 1 to 3 is denoted overall by
the numeral 1 and is shown in association with a camshaft 2 of an
internal combustion engine 3, which is shown here only in outline
and on the end of which that is associated with the illustrated end
of the camshaft 2 a chain case 4 (shown essentially only in
outline) is provided. Provided on this chain case 4, as an axial
extension of the camshaft 2 and situated opposite the latter, is
the actuator 5 associated with the camshaft adjuster 1. The
actuator is formed by an actuating magnet and is bolted onto the
outside of that end of the chain case 4 which is remote from the
internal combustion engine 3, as indicated at 6.
The actuator 5 formed by an actuating magnet interacts with the
armature 7 of a control spool 8, which is integrated into a central
screw in the form of a clamping screw 9, by means of which the
camshaft adjuster 1 is flanged onto the end of the camshaft 2, the
clamping screw 9, the control spool 8 of the camshaft adjuster 1
and the actuator 5 being coaxial with the camshaft 2.
Seated on the clamping screw 9 and clamped axially against the
camshaft 2 is the inner element 110 of the camshaft adjuster 1 and
associated with it is an outer element 111, which has teeth 12 on
its outer circumference, by means of which the camshaft 2 is driven
by the crankshaft (not shown here) of the internal combustion
engine 3 in a fixed relationship with respect to direction and
speed of rotation. The chain drive discussed and indicated here
could, of course, also be replaced by other types of drive
connection, such as toothed-belt drives or gear mechanisms.
Distributed over its circumference, the outer element 111 has
piston vanes 13, associated with which on the inner element 110 are
mating vanes 14, respective pairs of mating vanes 14 delimiting a
ring sector 15 in which a piston vane 13 of the outer element 111
is located, the outer element 111 forming, with the piston vanes 13
associated with it, as it were a vaned rotor which can be adjusted
relative to the inner element 110 over an angular range limited by
the mating vanes 14 of a ring sector 15.
Within each ring sector 15, the piston vanes 13 and the mating
vanes 14 delimit two working chambers 16, 17 that can be
pressurized hydraulically, more specifically under the control of
the control spool 8.
From FIGS. 1 and 3, it can be seen that the clamping screw 9 is
centered relative to the camshaft 2 by means of a centering collar
119 on the camshaft 2. The centering collar 119 is supported
directly on the circumference of the clamping screw 9. This
centering of the clamping screw 9 and the camshaft 2 relative to
one another in the region of the end adjacent to the camshaft 2
makes it possible to construct the inner element 110 and the outer
element 111 as flat discs. The result is that these have ends that
lie in planes perpendicular to the axis of the camshaft 2 and can
be covered by likewise flat covers 134, 135 designed as annular
covers. In conjunction with the axial clamping of the clamping
screw 9 relative to the camshaft 2, the centering collar 119
interacting with the circumference of the clamping screw 9 thus
allows direct alignment of the clamping screw 9 on the camshaft 2,
resulting in simplicity of manufacture and easily manageable
production of the camshaft adjuster 1 in terms of fitting
clearances. This applies especially also to the inner element 110
and the outer element 111 and to the annular covers 134, 135
covering the latter axially, since these components can all be
constructed as flat discs, at least as regards the interacting
surfaces, which allows narrow tolerances in combination with
simplicity of manufacture. This likewise makes it possible, where
appropriate, to clamp the covers 134, 135 against the inner element
110 and the outer element 111 without seals, although seals can be
incorporated into the interacting surfaces as annular seals without
any great outlay in such a solution, as indicated at 147. In
general, however, such seals are also superfluous because the
working pressures are relatively low and, even without seals, leaks
within the scope of the fine machining possible with surface
grinding are limited to a level that can be accepted if the
camshaft adjuster 1 is arranged in the chain case 4.
Pressure medium is fed to the respective working chamber 16 or 17
in a manner not shown specifically via a bearing location of the
camshaft 2 in the housing of the internal combustion engine and
radial holes 20 in the camshaft 2. From there, an axial passage 21,
22 leads via the camshaft 2 and the inner element 110 to an annular
space 23 in the inner element 110, this annular space overlapping
with radial holes 24 in the clamping screw 9. These holes open into
an annular space 25 in the control spool 8. The annular space is
situated between annular collars 26, 27 on the control spool 8
which delimit the annular space 25 axially.
Together with a further annular collar 28 offset in a direction
away from the camshaft 2, the annular collar 26 remote from the
camshaft 2 delimits another annular space 29, which is connected by
a radial connecting hole and an axial hole 30 to the receptacle 31,
which opens into the chain case 4 via a hole 32, the latter passing
through the bottom end of the receptacle 31, and a radial
connecting passage 33 that passes through the centering collar 119
of the camshaft 2.
The ring sectors containing the working chambers 16 and 17 are
closed off axially by the annular covers 134 and 135, which cover
areas of the end faces of the inner element 110 and the outer
element 111 and are held against the flat end faces of the inner
element 110 and the outer element 111 by axial clamping screws
38.
To fix the outer element 111 as a vaned rotor in its position
corresponding to the starting position of the internal combustion
engine, this generally 10 corresponding to a retarded position of
the camshaft 2, a locking element 39 in the form of a radial pin is
provided in the region of one piston vane 13 of the outer element
111. The radial pin is spring-loaded towards the inner element 110
and has associated with it a latching opening 40 in the inner
element 110. The latching opening 40 overlaps with a radial passage
41, which starts from an annular groove 42 provided in the inner
circumference of the inner element 110 and opens into the chamber
16. This annular groove 42 overlaps with radial holes 43 in the
axial wall of the clamping screw 9. The axial wall forms the guide
for the control spool 8 and delimits the receptacle 31 for the
control spool 8. Radial passages 44 (illustrated in broken lines in
FIG. 2) are provided in the inner element 110. These are offset
axially relative to the illustration in FIG. 1 and open into the
other working chamber 17. The radial passages 44 open into annular
grooves 45 that overlap with radial holes 46 in the wall of the
clamping screw 9.
When the internal combustion engine 3 is started, pressure medium
is supplied via the radial hole 20 in the camshaft 2 and passes via
the axial passages 21 and 22 into the annular space 25 of the
control spool 8. In accordance with the starting position, the
spool initially assumes a spring-loaded end position adjacent to
the camshaft 2 until, with the performance of the starting
operation, the actuator 5 is activated and the armature 7 is
attracted by the actuating magnet, with the result that the annular
space 25 is moved into overlap with the radial hole 43 in the
clamping screw 9 and, via the annular groove 42, with the radial
passage 41, and hence supplies the locking element 39 and the
chamber 16 with pressure medium. The locking element 39 is thereby
displaced counter to the spring force. The locking provided by the
locking element 39 is cancelled. The outer element 111 is pivoted
counter-clockwise (in relation to the illustration in FIG. 2) in
the direction of an advanced position of the camshaft 2.
Once the desired camshaft position has been reached by appropriate
control of the control magnet of the actuator 5, as a function of
the control of the engine, the annular collars 26 and 27 of the
control spool 8 are moved into overlap with the holes 43 and 46,
thus interrupting the supply of pressure medium to the chambers 16
and 17 as long as the camshaft is in its intended position. If
displacement occurs relative to this position, owing to leaks for
example, the necessary adjustment is performed by means of the
actuating magnet 5, which is adjusted accordingly, operating as a
continuous control element, e.g. as a proportional magnet, that is
by supplying or releasing pressure medium to or from one of the
chambers 16 and 17.
If the internal combustion engine 3 is switched off, the control
spool 8 moves back into the initial position. Here, the chamber 16
is connected to the return by the annular space 29. Thus, the
chamber 16 is emptied and simultaneously allows the pin forming the
locking element 39 to be pushed back into its locking position by
the spring force. In both end positions of the control spool 8, the
particular chamber that is not pressurized is open to the
return.
The configuration indicated provides a camshaft adjuster 1 which is
very short in the axial direction of the camshaft 2. The inner
element 110 is clamped axially against the camshaft 2 and at the
same time, centered by the clamping screw 9, the clamping screw 9,
for its part, simultaneously forms the centering means for the
inner element 110.
While the above detailed description describes the preferred
embodiment of the present invention, the invention is susceptible
to modification, variation and alteration without deviating from
the scope and fair meaning of the subjoined claims.
* * * * *